Method and Apparatus for Generating Input Images for Holographic Waveguide Displays

Abstract

An image generation device comprises: a spatial light modulator; a source of light; a beam deflector; an illumination waveguide and an image transport waveguide, each waveguide containing at least one switchable grating; and a coupler for directing scanned light into a first set of TIR paths in said illumination waveguide. A switchable grating in the illumination waveguide diffracts light onto said SLM, a switchable grating in said image transport waveguide diffracting image-modulated from the SLM into a waveguide path.

1 . An image generation device comprising:
 an image source configured to project collimated image-modulated light of a first wavelength over a field of view comprising a plurality of portions of the field of view; and   a waveguide supporting a plurality of switchable gratings each switchable between a non-diffracting state and a diffracting state and configured to couple said image-modulated light into said waveguide,   wherein said plurality of switchable gratings are configured to switch into their diffracting states in synchronism with the projection of one or more selected portions of said field of view by said image source,   wherein said plurality of switchable gratings in their diffracting states provide an aperture for coupling light into said waveguide, and   wherein said switchable gratings are configured to provide a different aperture for each said field of view portion.   
     
     
         2 . The apparatus of  claim 1 , wherein said switchable gratings exhibit high diffraction efficiency with no voltage applied and low diffraction efficiency with a voltage applied. 
     
     
         3 . The apparatus of  claim 1 , wherein said switchable gratings exhibit low diffraction efficiency with no voltage applied and high diffraction efficiency with a voltage applied. 
     
     
         4 . The apparatus of  claim 1 , wherein said aperture is replicated by total internal reflection within said waveguide. 
     
     
         5 . The apparatus of  claim 1 , wherein said switchable gratings are disposed in more than one layer. 
     
     
         6 . The apparatus of  claim 1 , wherein said field of view portions are projected in time sequence. 
     
     
         7 . The apparatus of  claim 1 , wherein said image source provides second wavelength light and said waveguide supports a second plurality of switchable gratings for diffracting said second wavelength. 
     
     
         8 . The apparatus of claim  7 , wherein one or more of said first plurality of gratings are switched into a diffracting state when said first wavelength image modulated light is projected and wherein one or more of said second plurality of gratings are switched into a diffracting state when said second wavelength image modulated light is projected. 
     
     
         9 . The apparatus of  claim 1 , wherein said waveguide is a component of a waveguide display. 
     
     
         10 . The apparatus of  claim 1 , wherein said waveguide further comprises at least one set of gratings selected from the group of: gratings providing beam expansion in at least one dimension, gratings providing extraction of said light from said waveguide, gratings providing field of view tiling, gratings with spatially varying refractive index modulation, and gratings with spatially varying thickness. 
     
     
         11 . The apparatus of  claim 1 , wherein said switchable gratings each have a unique angular diffraction characteristic. 
     
     
         12 . The apparatus of  claim 1 , further comprising at least one of a collimating lens and a despeckler. 
     
     
         13 . The apparatus of  claim 1 , wherein said waveguide is selected from the group of a curved waveguide and plastic waveguide. 
     
     
         14 . The apparatus of  claim 1 , wherein said image source employs a light source comprising one of a laser or a light emitting diode. 
     
     
         15 . The apparatus of  claim 1 , wherein said switchable gratings are recorded in a liquid crystal and polymer holographic recording material. 
     
     
         16 . The apparatus of  claim 1 , wherein said switchable gratings include at least one grating selected from the group of: a uniform modulation HPDLC grating, a non-switching HPDLC grating a reverse mode HPDLC grating and a surface relief grating. 
     
     
         17 . The apparatus of  claim 1 , wherein said image source comprises:
 a spatial light modulator;   a source emitting first wavelength light;   a beam deflector for forming said light into a scanned beam;   an illumination waveguide containing at least one switchable grating disposed in at least one layer;   an image transport waveguide containing at least one switchable grating disposed in at least one layer; and   a coupler for directing said scanned beam into a first set of total internal reflection paths in said illumination waveguide;   wherein said at least one switchable grating in said illumination waveguide is configured to diffract light out of said first set of total internal reflection paths onto said spatial light modulator;   d) wherein said at least one switchable grating in said image transport waveguide is configured to diffract the image-modulated light from said spatial light modulator into a second set of total internal reflection paths in said image transport waveguide.   
     
     
         18 . The method of  claim 17 , wherein the extent of said at least one grating along said image transport waveguide defines a coupling aperture, and wherein said coupling aperture defines a numerical aperture for each pixel of said spatial light modulator. 
     
     
         19 . A method of viewing an image comprising the steps of:
 providing an image source for projecting collimated image-modulated light of a first wavelength over a field of view comprising a plurality of portions of the field of view, and a waveguide supporting a plurality of switchable gratings each switchable between a non-diffracting state and a diffracting state and configured to couple said image-modulated light into said waveguide;   providing an output grating for extracting light from said waveguide for viewing;   projecting a first field of view portion;   switching a set of the plurality of switchable gratings into their diffracting states to form an aperture for coupling said first field of view portion into said waveguide;   coupling said first field of view portion into a total internal reflection path in said waveguide; and   extracting said first field of view portion light from said waveguide via said output grating.   
     
     
         20 . The method of  claim 19 , further comprising the steps of projecting a second field of view portion and repeating the steps of projecting, switching, coupling and extracting.